1. Field of the Invention
The present invention relates in general to a parts cleaner, in which workpieces are carried within baskets mounted on a rotating framework and submersed in cleaning fluid.
2. Description of the Related Art
Systems have been proposed for treating or washing workpieces with a fluid, in particular for cleaning and/or rinsing metallic workpieces that are being processed through complex heat treatment installations. These heat treatment installations may include, for example, vacuum heat treatment furnaces, push-through-furnaces, roller hearth furnaces, vertical retort furnaces or multi-purpose chamber furnaces. These furnaces perform blank annealing heat treatment and various other annealing processes. The furnaces also perform hardening processes and diffusion processes, such as nitriding, nitrocarburization, carbonitriding and carburization.
Prior to heat treatment, the workpiece must be thoroughly cleaned. Such precleaning is of particular importance after the workpiece has been machined, such as with a forge, a lathe, a mill or grinder. During machining, the workpiece becomes shrouded in foreign matter such as cooling lubricant, grease, lapping pastes, pigments, hardening oils, dusts and metal fragments. This foreign matter must be removed entirely before the surface of the workpiece may be treated by the above-noted heating processes. For instance, during the hardening process, nitrogen and/or carbon penetrate the workpiece surface through diffusion. However, foreign matter on the workpiece surface retards or prevents the diffusion process. Consequently, the resulting workpiece is not hardened or only partially hardened in regions covered with the foreign matter.
To avoid this problem, systems have been proposed for cleaning the workpiece once it has been machined but before its surface is treated. Often the workpiece includes a very complex contour with multiple recesses, grooves and the like, which are very difficult to clean entirely. To ensure that the workpiece is adequately cleaned, conventional cleaning systems have utilized cleaning solvents that are quite harsh and damaging to the environment. More recently, cleaning systems have been developed to be environmentally safe, by utilizing environmental sound cleaning fluids, such as soapy water. However, in order to clean the recesses, grooves, and the like sufficiently with these cleaning fluids, the environmentally sound cleaning systems must introduce the cleaning fluid with great force.
Alternatively, cleaning systems have been proposed that use a washing vessel filled with an immersion bath substantially covering the workpiece and having a temperature between 50.degree. C. and 90.degree. C. Once the washing vessel is closed, it is evacuated to obtain a vacuumous chamber having a pressure below the saturation vapor pressure of the cleaning fluid. This reduction in pressure causes the cleaning fluid to boil. The vacuum and boiling effect are maintained for a desired period of time until the workpiece is cleaned, after which the pressure is relieved, the cleaning fluid is discharged and the workpiece is removed. To achieve a vacuum chamber and to retain the boiling cleaner fluid, the washing vessel is sealed once the workpiece is loaded therein.
Further, it is desirable to clean as many workpieces in each wash cycle as possible. In keeping with this goal, one conventional parts cleaner has been introduced, in Europe, that includes a washing vessel which receives a parts tumbler. The parts tumbler includes a rotisserie-like construction with a central framework rotated about its axis on two trunnions in a bearing arrangement. The rotisserie includes two baskets fastened to opposite ends of the central rotating framework distal-proximate from one another. The baskets loosely contain the workpieces such that the pieces constantly tumble as the framework rotates, thus the name "parts tumbler". One end of the parts tumbler includes a drive shaft extending along the axis of rotation and outward from the baskets. The shaft is removably fastened at one end, through a coupling, to the framework and securely fastened at an opposite end to a cog or a sprocket which engages a driving mechanism. The drive mechanism induces rotation of the sprocket and the shaft and, ultimately, of the framework and the baskets. During operation, the tumbler must be removed from the vessel to load and unload the parts baskets. Once the parts are loaded within the baskets and the tumbler is loaded within the vessel, the washing chamber is sealed, flooded with cleaning fluid and evacuated until the cleaning fluid begins to boil. During cleaning, the tumbler is rotated by the driving mechanism.
However, in this conventional parts cleaner, the drive mechanism must remain isolated from the cleaning fluid, and thus outside the washing vessel. Accordingly, the driving mechanism and sprocket were positioned outside the vessel, with the shaft extending through a wall of the vessel. A water-tight seal was required between the vessel wall and the point at which the shaft extended therethrough, to prevent leakage of cleaning fluid during operation and to enable decompression of the vessel. To maintain this water-tight seal, the tumbler was formed with a coupling between the drive shaft and the framework thereby rendering the tumbler separable from the driving mechanism each time the tumbler was removed from the vessel to empty the parts baskets. This coupling assembly hindered removal of the tumbler from the vessel. Also, once the tumbler was removed from the vessel, it was unable to rotate the tumbler since the driving mechanism had been disconnected.
The need remains in the parts cleaning industry for improved design and operating techniques to address the problems and drawbacks heretofore experienced. The primary objective of this invention is to meet this need.